Start-stop regenerative telegraph repeater



Jan. 23, 1945. E. F. WATSON 2,357,910

START-STOP REGENERATIVE TELEGRAPH REPEATER Filed July 19, 1941 2Sheets-Sheet 1 POL AR AAA -IIIIIHI" Eff WATSON ATTORNEY .A

Patented Jan. 23, 1945 UNITED STATES PATENT OFFICE START-STOPREGENERATIVE TELEGRAPH REPEATER Application July 19, 1941, Serial No.403,082

12 Claims.

This invention relates to improvements in startstop regenerativetelegraph repeaters and more particularly to arran ements for improvingthe operation of said repeaters in the presence of interferingconditions in the line circuit.

A mechanical type of start-stop regenerator unit has been in extensiveuse for some time in half-duplex telegraph repeaters, particularly inteletypewriter service. Two such regenerator units are used in therepeater, one for transmission in one direction and the other fortransmission in the opposite direction. When the repeater is arrangedfor half-duplex operation, that is; for operation in one direction at atime, provision is made for locking the inactive side in its stopposition by means of off-normal contacts in the unit operating in theactive side so that all impulses of a signal series representing acharacter will be sent before the other unit is permitted to operate.

A regenerator unit of the type referred to is disclosed in U. S. Patent2,105,173, issued to Zenner et al. on January 11, 1938, and referencemay be had to this disclosure for details of its mechanism andoperation.

The unit comprises a receiving magnet, responsiv-e to incoming signals,and transmitting contacts for reproducing the received signals andretransmitting them into the outgoing line circuit. An intervening cammechanism, motordriven through a friction clutch and stopped once aftereach revolution, controls a plurality of operating levers and thearrangement is such that the magnet determines Whether the regeneratorcontacts should be in marking or in spacing position and the rotatingmechanism determines at i which time the contacts should be moved fromone position to the other. outgoing signals Will have marking andspacing impulses in conformity with the incoming signals and theoutgoing impulses will be timed to be of uniform length.

As is well known, the start-stop signals comprise a stop and a startimpulse and five, or sometimes six, character impulses. The stop impulseusually is of marking and the start impulse of spacing characteristic.

For the purpose of maintaining successive outgoing signal series inisochronism with incoming signal series, the regenerator unit isequipped with a stop mechanism adapted to stop the cam mechanism duringthe stop impulse and to release it under control of the. receivingmagnet in response to the succeeding start impulse.

The two regenerator units operate between two sections of a single linecircuit and each section In this manner the may include a sensitivepolar receiving relay for control of the associated receiving magnet.In' a preferred form the locking arrangement referred to above iseffective in p'reventing one re- 5 ceiving relay from starting itsassociated unit during the reception of a signal series by the otherreceiving relay and the locking circuit for the inactive relay includesthe contacts of the active relay and the off-normal contacts of theactive unit. These contacts cooperate in looking the inactive relayexcept for a portion of each stop impulsepassing through the activeside, thereby permitting the inactive side to respond to a sig-.

nal, such. as a break signal, from its line circuit 1 during thisunguarded period. a

A circuit arrangement of this type has been disclosed in U. S. PatentNo. 2,243,215 issued on May 27, 1941, to W. V. K. Large, and referencemay be had particularly to Fig. 2 of that disclosure.

2 practice in commercial circuits to provide hit indicators that can beconnected'in each line section. These indicators may be of differenttypes but have the common characteristics of responding separately toall pulses passing in each direction in the line circuit underobservation and of giving an indication, which may be visual, for eachresponse. Thus an observer will find one meter in the indicator activelyresponding to a message in a given direction and another associatedmet-er remaining inactive during the transmission of the same message.Hits passing in the same direction as the message cannot be observed inthis manner, whereas hits passing in the opposite direction will givereadily observed indications on the inactive meter. In this manner toothe message and occurring during the unguarded portion of a stop impulsefrequently give erroneous indications on the hit indicator. Such a hitmay cause the inactive receiving relay in the repeater circuit to startthe inactive unit which then would send a spacing impulse back into theoriginating line circuit-thereby giving a false indication on theinactive hit meter. Thus the observer of the hit meters may be confusedas to the origin of the hit.

Other provisions are made in the commercial circuits for supervision oflong spacing conditions, such as break signals. For this purpose it isimportant that the open condition remain uninterrupted by the repeatercircuit.

It is therefore an object of the invention to prevent the reflectioninto the originating line of hits arriving on that line by a start-stopregenerative repeater circuit, 50 that line trouble may more quickly belocated.

It is a more specific object to guard the inactive side of a two-wayrepeater during the otherwise unguarded interval during the stop impulseto prevent false operation due to a hit.

It is another specific object to thus guard the inactive sidesubstantially without interfering with the normal modes of operation ofthe regenerative repeater circuit.

An arrangement for the attainment of these objects has been disclosed ina copendin application for U. S. Patent Serial No. 331,251, filed onApril 23, 1940, by F. H. Fox which has issued as Patent No. 2,252,622,on Aug. 12, 1941. This arrangement includes certain contacts which forthe purposes of Foxs invention were added to the cam mechanism of eachregenerator unit of a repeater.

It is a further object of the invention to provide an arrangement forpreventing the reflection of bits which will not require mechanicalalteration of the regenerator units in the repeater.

In accordance with a feature of the invention the prevention ofreflection is secured entirely by special control applied to the localtiming circuits as distinguished from the signal carrying line circuitsin the repeaters, namely, by control of the operation of theregenerator'magnet to prevent untimely starting of the inactive unitduring the unguarded period.

In accordance with a more specific feature the special control referredto is exerted by a delay circuit which is timed to bridge the usualunguarded period by preventing the inactive regenerator magnet fromstarting its unit in response to a false starting pulse in the outgoingline circuit produced by false operation of the active unit due to a hitin the incoming line circuit during the stop pulse. The arrangement ofthe delay circuit is, however, such that a long interruption, such as abreak signal, in the outgoing line circuit will be retransmitted intothe incoming line circuit after the activ unit has completed its falseoperating cycle and reestablished the normal unguarded period forpermitting the inactive unit to start.

In accordance with a still more specific feature the delay circuit foreach unit includes a timed relay, such as a slow-release relay, which isadapted to extend the duration of the guard condition, established bythe active side of the repeater during its operating cycle, to cover theduration of a normal stop impulse at the end of each signal series ofimpulses representing a character.

The invention will now be described more in detail as to its structureand operation as applied to two alternative preferred embodiments. Thefollowing description should be read in connection with the attacheddrawings which each shows a circuit diagram of a repeater stationincluding two regenerator units of the general type, shown in the Zenneret 211. patent referred to above. The regenerator units are shown indiagrammatic form with elements corresponding to those of the devicedisclosed by Zenner et al. and numbered to correspond to the numeralsidentifying the elements in the Zenner et al. patent.

It should, of course, be understood that Whereas the embodiments shownin the drawings each includes mechanical regenerator units the inventionmay readily be adapted for operation with other types of start-stopregenerator units, such as the well-known type using segments and brushcontacts. It should further be understood that whereas the disclosedembodiments each include a circuit arrangement similar to that of Fig. 2in the copending application by Large, referred to above, other circuitarrangements, such as those shown in Fig. 1 or 3 of the Largedisclosure. may be used for the purposes of the invention.

In the drawings Figs. 1 and 2 show the invention in two differentembodiments, respectively, applied to identical repeater circuits of thetype disclosed in the patent to Large, referred to above. In Fig. 1 thetimed relay controls a circuit for producing a transient control currentduring the unguarded period, and in Fig. 2 the timed relay controls asimple direct currentflow during the unguarded period.

The repeater circuits and their units being identical in Figs. 1 and 2they will both be described together hereinafter, and correspondingreference numerals will be applied to corresponding parts. The specificcircuit elements for carrying out the principles of the invention andtheir operation with the repeater circuits will thereafter be describedseparately with reference to the two embodiments, respectively, by meansof separately assigned reference numerals for the corresponding parts.

Referring now to the repeater circuit diagram shown in the drawings thesystem comprises a repeating station with relay equipment for halfduplexoperation between two line sections LW and LE which may terminate insubscribers loop circuits including the usual receiving and transmittingequipment at each subscribers station. The repeating station comprisestwo regenerator units 20! and 292, one for each direction oftransmission. Two polar relays 203 and 204 having operating and biasingwindings are associated with the regenerator units 20! and 292,respectively. The loop circuits will normally be closed and the normalline current will act to operate relays 203 and 254 to marking. Aspacing signal is transmitted by opening either one of the loop circuitsWhich causes the relays 203 or 204 to be operated to spacing by theirbiasing windings which are normally connected to a predeterminedpotential through potentiometers 2 H and 2 i 2, respectively.

Each regenerator unit will be assumed to be of the type disclosed in thepatent to Zenner et al., referred to above, and comprises a receivingmagnet M controlled by its associated receiving relay, transmittingcontacts T controlled by the magnet M and the cam mechanism of the unitfor operation into marking or spacing position, and off-normal orlooking contacts L controlled by the cam mechanism.

The transmitting contacts T are included directly in the respective linecircuits and thus repeat the signals directly into the subscribersloops, the outgoing impulses passing through the operating winding ofthe receiving relay in the outgoing circuit and tending to operate thatrelay. The polar relays are, however, prevented from responding tooutgoing signals, except 'for short intervals during each stopcondition, by the application of a locking potential to thepotentiometer connected to the biasing winding of the relay, the lockingpotential being applied either from the spacing contact of the activepolar relay or from the locking contact of the active regenerator unitor both; this locking potential is of a polarity opposite to thatpermanently applied to the other end of thepotentiometer and causes thecurrent to reverse in the biasing winding.

Referring now particularly to the details of each regenerator unit, thecams 2|, 22, 23, 24 are mounted on a common cam :sleeve intermittentlydriven through a friction clutch 3| by any suitable continuouslyrotating power supply ;P. The stop cam 2i cooperates with a stop latch34 for stopping the cam sleeve in stop position; the stop latch is inturn controlled by armature 1100f magnet M so that when the armatu-re isreleased by magnet M the latch 34 will permit the stop cam 21 and camsleeve 20 to rotate.

The armature 40 has a spring for retracting the armature and the magnetMis not of a sufficient strength during :a marking impulse to attract thearmat-ure, but is of sufficient strength to hold the armature attractedduring the marking impulses. The armature 40 cooperates with a fluttercam 22 with projections properly distributed about its periphery forraising the armature 40 against the spring 55 to present the armature tothe magnet M. It at such a time mag net M is energized, as during amarking impulse, the armature 40 remains attracted. If, however, themagnet is deenergized, as during a spacing impulse, the armature will beretracted after the passing of the cam projection on cam 72.2.- Thearmature 40 also carries a contact operating member 85, schematicallyshown as being flexible so that the member 65 may be locked againsteither the marking contact m or the spacing contact s by means oflocking lever 11 while the the arm 65 is released by the locking leverT! i which forms part of the lock arm 5']. The lock arm 57 is normallyin engagement with a lock cam 24 by means of a spring 81 and duringrotation of the cam sleeve will be raised :at pre-' determined intervals.by the projections on the lock cam 24, thereby removing the lockinglever 11 from engagement with the flexible contact 2 arm and permittingthe latter to swing into engagement with either the marking or thespacing contact as determined by the position of the armature 40. Thedistribution of the projections on the flutter cam 22 and lock cam 24 issuch that for any particular impulse of .a signal impulse series thearmature 40 will first be presented to the magnet 'M'and will be held ordropped by the magnet, as the case may be, whereupon the lock arm 57will be operated to permit the flexible contact arm 65 to, if necessary,change from one position to the other,

An ofi-normal cam 23 has a single projection whichin stop positionoperates the locking lever 60 against the tension of a contact spring:to open the locking contacts L, thereby opening the holding circuit forthe polar relay connected in the output circuit of the unit.

Assuming that a message is to be transmitted from the line West LW tothe line East LE, a start impulse is received over the line circuit LWthrough the operating Winding of relay 203 and over the closed contactsT of the regenerator unit 202. Relay 203 responds by moving to spacing,thereby breaking the current in magnet M .of the unit 20! and alsoapplying negative potential to the low resistanc'e end of thepotentiometer 2l2, the high resistance end of which is connected topositive potential, so that the current in the biasing winding of relay204 will reverse and hold this relay in marking position. The unit 201will be started by the release of armature 40 and immediately thereafterthe locking contacts L will be operated to their alternate positionthereby applying negative potential to the potentiometer 212 and thuspreventing relay-.204 and unit 202 from operating until unit 2! againreaches its stop position.

After a short interval the lock arm 51 is elevated by the firstprojection on cam 24 to unlock the flexible contact arm 65 which quicklymoves to spacing position due to the stored-up tension produced by thearmature when the latter was dropped. The transmitting contacts T thuswill be opened and will transmit a spacing impulse into the loop LEwithout afi'ecting relay 204.

The circuit will remain in this condition until a marking impulse isreceived over loop LW which will operate relay 203 to marking therebyenergizing magnet M of unit 20 I. However, as the cam sleeve revolvesthe flutter cam 22 will raisethe armature 40 once for each impulseperiodthereby presenting the armature to the magnet M for holding ordropping after each cam projection has passed. Cam Z4 raises the lockarm '5] once for each impulse period shortly after the armature has beenpresented and has assumed its position in accordance with thecharacteristic of the pulse. Thus the transmitting contacts 'I' arepermitted to open or close the line circuit LE in accordance with theposition of armature 40, thereby transmitting impulses from LW into theoutgoing circuit LE.

When the stop impulse arrives, relay 203 moves to marking therebyenergizing magnet M of unit 20l. When the stop projection of cam 22 nextpresents the armature to the magnet the armature will be held attracted,thereby placin the stop latch 34 in the path of the cam 21 for stoppingthe unit. Shortly thereafter the stop pro- Jection on cam '24 releasesthe transmitting contacts T which then move to marking, or remain inmarking as the case may be, for transmission of a. stop impulse into theloop circuit LE. The contacts '1 will thereafter be locked While theunit moves to stop position and until the unit is again started,whereupon the start projection of cam 24 again will release the contactsT. The

circuit is thus restored to normal condition as shown in the drawings.

It will be noted that the negative guard potential applied by relay 203topotentiometer 2H3 is disconnected during the entire length of theincoming stop impulse and that the negative guard potential applied bylocking contact L of unit 2M to the potentiometer 212 is disconnected bythe off-normal cam 23 for an interval from shortly after the beginningof the outgoing stop impulse until shortly after the next starting ofthe unit. Relay 204 therefore is permitted to operate to spacing themoment off-normal cam 23 opens the locking contacts L until the momentrelay 203 operates to spacing in response to the next start impulse.This unguarded interval is provided to permit a break signal from lineLE to start the regenerator unit 202 for placing a long opening on theline circuit LW, thereby notifying the transmitting subscriber that theother party wish es to cut in.

Referring now more particularly to Fig. l of the drawing, the systemincludes certain circuit details serVing the purposes of the nvention.Thus a slow releasing relay 32! has its winding included in the batterylead from negative battery to the locking contacts L of unit 20l andthus will be in operated condition while the contacts L are closedduring each revolution of the unit. A similar relay 33l is included inthe battery lead from positive battery to the contacts L of unit 202.Relay 32! when operated closes a circuit from plus battery through acondenser 322 and resistance 323 to the magnet M of unit 202. Thiscondenser circuit is normall short-circuited over the marking contact112 of relay 204. A similar condenser circuit including condenser 332and resistance 333 is controlled by relay 33! and is short-circuited byrelay 203 in marking position.

Under normal operating conditions of the regenerator unit relay 203 willoperate magnet M to start the unit; shortly thereafter contacts L closeto operate relay 32l through potentiometer 2i2. Wtih relay 204 inmarking the operation of relay 32! has no effect. When unit 20! returnsto normal, contact L open the circuit for relay 32! which now will holdits contacts closed for an interval somewhat longer than a characterlength if contacts L remain open. If during-this interval relay 204should operate to spacing, under conditions which will be explainedbelow, the uncharged condenser 322 will be included in the circuit fromnegative battery to magnet M of unit 202 and the resulting chargingcurrent to condenser 322 will temporarily energize magnet M sufficientlyto delay the dropping of armature 40 and the starting of the unit 202for somewhat longer than a normal length stop impulse. If relay 204should return to marking soon enough, the normal energizing circuit formagnet M will be restored without starting of unit 202.

In the case of a break signal being transmitted from line East to theunit 202, relay 204 will'operate-to spacing at the beginning of the nextunguarded period, and after condenser 322 has become charged throughmagnet M of unit 202 this unit will be started and will keep on rotatingso long as the spacing condition of the break signal is maintained,thereby holding the line LW open for the duration of the break signal.Condenser 322 will be discharged again at the time normal transmissionfrom line LW is resumed. During transmission from line LE condenser 322will be disconnected when slow release relay 32! opens its contacts. Asis well known, the break signal may be sent during transmission in theopposite direction as a request to the other station to stop sending, ora similar spacing signal may be sent through an idle line to call orstart the other station.

When a hit occurs on line LW during transmission from line LW to lineLE, as described above, a spacing condition will be imposed on theincoming end of the line circuit LW causing relay 203 to operate tospacing for the duration of the hit and the magnet M of the rotatingunit 20! will drop the armature each time it is presented during the hitand will cause corresponding spacing impulses to be transmitted into theline LE. Such hits may interfere with the message in line LE .but cannotbe observed on the hit meters for either the active or inactivedirection. A hit on the line LE occuring during transmission from lineLW may also interfere with the reception of the message in line LE butcan be properly observed on the inactive hit meter associated with theline circuit. If long enough, such a hit may start unit 202 in themanner of a break signal, as described above, in which case it couldalso be properly observed on the inactive hit meter associated with lineLW.

A special condition arises, however, when a hit occurs on the incomingcircuit during a stop pulse and particularly when the hit is present atthe time the transmitting contacts T are unlocked for operation tomarking in response to the stop impulse.

Relay 203 thus will be operated to spacing by the hit on line LW therebycausing the magnet M to drop armature 40 after it has been presented bythe stop projection on cam 22 with the result that the transmittingcontacts T, when released by locking cam 24 will move to spacing insteadof moving to marking as in the case of an uninterrupted incoming stopimpulse. The unit 20! will thus fail to stop and the contacts T willremain in spacing during the subsequent start impulse and at least;until the armature 40 has been presented to magnet M by a projection oncam 22. If the hit be long enough to last into the incoming startimpulse, the receiving relay 203 would remain in spacing and there wouldbe no unguarded period for relay 204 which thereafter would remainlocked by contacts L of unit 20| until the next stop impulse irom lineLW. However, when the hit ceases before the beginning of the next startimpulse, the unguarded period for relay 204 may be as long as duringnormal operation.

In the absence of the condenser circuit 322, 323 provided in accordancewith the invention and described above, the opening, due to the hit, orthe line circuit LE by contacts T of unit 20! extending into theunguarded interval of the stop period, i. e., beyond the passing of thehit and the return of relay 203 to marking, would cause relay 204 tomove to spacing and to start its associated regenerator unit 202. Aguard potential would immediately be supplied to potentiometer 2H forlocking relay 203 in marking position during a revolution of unit, 202,and when the transmitting contacts of unit 202 were released by thestart projection on cam 24 a spacing impulse would be transmitted intoline circuit LW. Since transmission from line LW would continue thespacing pulse from unit 202 against the prevailing direction oftransmission would be indicated on the hit indicator as a hitoriginating in line circuit LE, which would be erroneous.

With the condenser circuit 322, 323 provided in accordance with theinvention, the starting of the unit 202 in response to a short operationof relay 204 to spacing is prevented, as described above, and the linecircuit LW remains closed at the contacts T of unit 202. The erroneoushit indication under the special condition just described is thusprevented and the location of line faults is expedited.

Thus when a hit occurs on line LW and is present when the transmittingcontacts T of. unit are unlocked by the stop projection; on cam 24 thesecontacts will be locked in spacing as described above, and the linecircuit LE will be opened; with relay 203 still in spacing during thehit relay 204 is prevented from operating to spacing. However, when,after the passing of the hit, relay 203 returns to marking theunguardedperiod commences and relay 204 operates to spacing. As alreadydescribed, the unit 202 is temporarily prevented from being started bythe condenser circuit 322, 323. Unit 20! continues its rotation throughits stop position and in running into its next rotationimmediatelycloses its contacts L thereby applying the guard potential topotentiometer H2 and operating relay 204 back to marking and energizingrelay 32i for discharge of condenser 322. With the proper timingconstants of the circuit 322,323 the unit 202 will be prevented fromstarting under these conditions before the return of re-' lay 204 tomarking. Thus the hit in line LW will not be reflected back into thatline by the unit 202 and the inactive meter in the hit indicator willremain unaffected by the hit in the active direction. However, sincearmature '40 of unit 20! remains retracted due to the hit and the camsleeve fails to stop, there may be some interference with thetransmission of one or two characters into the loop circuit LE.

Referring more particularly to Fig. 2 of the drawings, the circuitelements fori preventing reflection of hits includes slow release relay421 and 431. In this arrangement the winding of relay 421 is connecteddirectly 11 the lead to potentiometer 212 so that this relay will beoperated when relay 203 goes to spacing in response to a start pulsevand will remain operated over contacts L of unit 20! during. the entirerevolution of this unit. The contacts of relay 42| are connected tosupply negative potential to magnet M of unit 2021and are normallyshortcircuited by the marking contacts, of. relay 204. Relay 43 issimilarly connected for operationby relay 204 and unit 202 for controlof magnet M of unit 20L From the description given above inconnectionwith Fig. 1 it will be immediately apparent that. the presenceof relays 42! and 43I will have no effect upon the operation of the.repeater circuit except under the special condition, referred to above,when a hit occurs on the incoming circuit during. a stop impulse and ispresent at the time the transmitting contacts T are unlocked for returnto marking in response to the stop impulse, the hit passing before theend of the stop impulse, so that there will bean unguarded period.

Assuming such a hit to occur in line LW, relay 203 will be in spacingposition when armature 40 of unit. 20] passes off the stop projection oncam 22. The contacts T operate to spacing and open the line circuit LE.Relay '42! has been operated and relay 204 has been held in marking bythe. contacts L of unit EM and are now also being held by relay 203.inspacing.

When the hit ceases relay 203 returns to marking and when the lever 60is raised by the stop projection on cam 23 of unit 201 contacts L areopened. At such time relay 42! commences its slow release and relay 204operates to spacing due to the open condition ofline LE at contact Tof'unit 20!. Without the relay 42I the operation of relay 204- tospacing would start the unit 202. However, with the relay 421 includedin the circuit, the magnet. M remains temporarily energized over thecontacts: of. relay 42! after relay 204 has. opened its markingcontacts. Relay 421 is: timed to open its contact. after an intervalsomewhat longer than the duration of usual stop impulses. As the unit2.0l. continues its rotation. into the. next cycle, the contacts L willclose: andwhen. the next. start impulse: arrives over the line LW thespacing contacts on relay 203 will also close: thereby holding relayi2ienergized. In this manner false starting of the inactive. unit- 202" andreflection into the incoming circuit of: a hit in that: circuit isprevented and erroneous indications on the hit'indicator are prevented.

Inasmuch as the two' regenerator units of. the repeater station aresimilarly connected into the circuit, operation or the system duringtransmission from the line LE. to. the. line: LW will proceed in thesame manner'as described above fortransmission in the oppositedirection. Also. the prevention. of a false indication by the-hit metersdue to a hitv on line LE during a stop impulse is accomplished: in thesame manneras described above for a: similar hit on the'line circuitLW.-

Whereas the invention has been describedabove. as being applied to acircuit arrangement in which the: receiving relay in the inactive sideis locked against operation except during the unguarded period, itshould be: understood that the invention is readily adaptable to acircuit arrangement in which the star-ting of the inactive unit isprevented, except duringthe unguarded period, bythe application of aguard potential or other provision effective during the revolution ofthe active unit in looking the inactive magnet. Examples of such systemsare shown in 'Figs. I and 3m the patent to Large referred to above.

What is claimed is:

l. A two way start-stop telegraph repeater system connected between twoline circuits and comprising a west and an east regenerative repeater'alternately active and inactive to, one at a time, repeat start-stopcode impulses incoming from west and east into-the east and west linecircuits, respectively, each of said repeaters including receivingWinding means; timed repeating contact means controlled as to' code bysaid recei-ving winding means, guard contact meansconnected to lock theother of said repeaters against operation during the operating cycle ofthe active repeater except for an unguarded period during each stopimpul'seincoming to said activerepeater, and circuit controlmeans-connected-to control the starting of said" other repeater andadapted to be operated into'one of two conditions in response to thelocking ope-ration of said guard contact means and adjustable toautomatically remain insai'd one condition for a predetermined timeinterval duringsaid unguarded period to delay starting of said otherrepeater;

2. A two-way start-stop telegraph repeater system connected betweentwoline circuits and comprising a west and an east regenerativerepeate'r' alternatelyactive'and inactive to,- one at a time; repeatstart-stopcode impulses incoming from" westand east into theeast andwest l-ine circuits; respectively, each of said repeaters in-- cludingreceiving winding means, timed repeating' contact meanscont'rol-led a'sto" code by said receiving winding means, guard contact means connectedto lock the other of' said repeaters against operationduring'theoperating cycle of the active repeater except for an unguardedperiod during each stop-impulse incoming tosaidactive repeater, andcircuit control means connected to control the starting of said otherrepeater and adapted to be operated into one of two conditions by saidguard contact means during locking of the other repeater and adjustableto temporarily remain in said one condition after the beginning of saidunguarded period to delay starting of said other repeater by a startcondition impressed upon said repeater system from either of said linecircuits.

3. A two-way start-stop telegraph repeater system connected between twoline circuits and comprising a West and an east regenerative repeateralternately active and inactive to, one at a time, repeat start-stopcode impulses incoming from west and east into the east and west linecircuits, respectively, each of said repeaters including receivingwinding means, timed repeating contact means controlled as to code bysaid receiving winding means, guard contact means connected to lock theother of said repeaters against operation during the operating cycl ofthe active repeater except for an unguarded period during each stopimpulse incoming to said active repeater, and circuit control meansconnected to control the starting of said other repeater and connectedin a circuit to said guard contact means to be operated into one of twoconditions in response to the locking operation of said guard contactmeans for in said one condition placing a supplementary guard conditionon said other repeater, said circuit control means being timed tomaintain said guard condition for the usual duration of the saidunguarded period under normal transmission to prevent starting of saidother repeater except during an unguarded period of greater than apredetermined duration.

4. A two-way start-stop telegraph repeater system connected between twoline circuits and comprising a west and an east regenerative repeateralternately active and inactive to, one at a time, repeat start-stopcode impulses incoming from west and east into the east and west linecircuits, respectively, each of said repeaters including receivingwinding means, timed repeater contact means controlled as to code bysaid receiving winding means, guard circuit means including contactmeans for locking the other of said repeaters against operation duringthe operating cycle of the active repeater except for an unguardedperiod during each stop impulse incoming to said active repeater, asupplementary guard circuit, and circuit control means includingslow-acting relay means having contacts for control of the starting ofSaid other repeater and being connected to operate in response to thelocking operation of said guard circuit means for closing by itscontacts said supplementary guard circuit for said other repeater duringa complete operating cycle of said active repeater including saidunguarded period of a predetermined maximum duration to prevent startingof said other repeater within said unguarded period.

5. A two-way start-stop telegraph repeater system in accordance withclaim 4 in which said supplementary guard circuit is connected, whenclosed, to maintain said receiving winding means energized in said otherrepeater for said maximum duration of the unguarded period to preventsaid starting in response to a start condition impressed upon saidrepeater system from either of said line circuits.

6. A two-way start-stop telegraph repeater system in accordance withclaim 4 in which said supplementary guard circuit, when closed, in-

eludes capacitance means to establish a transient current forenergization of said receiving winding means in said other repeater inresponse to a start condition impressed upon said repeater 5 system fromeither of said line circuits during said unguarded period, saidtransient current being of sufiicient strength for said maximum durationto prevent starting of said other repeater.

7. A two-way start-stop telegraph repeater system connected between twoline circuits and comprising a west and an east regenerative repeateralternately active and inactive to, one at a time, repeat start-stopcode impulses incoming from west and cast into the east and West linecircuits, respectively, each of said repeaters including a receivingline relay responsive to impulses in the associated line circuit, arotary start-stop regenerator unit having mechanically timed repeatingcontacts for producing impulses in the associated line circuit andhaving a control magnet responsive to said line relay to start and stopsaid unit for each cycle of operation and to control said repeatingcontacts as to impulse characterization, locking circuit means includingcontacts on said line relay in start condition and including off-normalcontacts on said unit and connected for locking of said line relay ofthe inactive repeater in its stop position during the operating cycle ofthe active repeater to prevent starting of said unit in the inactiverepeater during said cycle except for an unguarded period during eachstopimpulse incoming to the active repeater, a supplementary guardcircuit, and circuit control means including a slow-acting relayconnected to operate in response to said locking by said locking circuitmeans and having contacts for closing said supplementary guard circuitfor said control magnet in the inactive repeater continuously during theoperating cycle of the inactive repeater and during said unguardedperiod of a predetermined maximum duration to prevent starting of theinactive unit by the inactive line relay in response to a start impulsecondition in either of said line circuits during said unguarded period.

8;. A two-way start-stop telegraph repeater system in accordance withclaim 7 in which said guard circuit is connected to, when closed,maintain the inactive control magnet in stop condition independently ofoperations by the line relay in the inactive repeater during saidunguarded period.

9. A two-way start-stop telegraph repeater system in accordance withclaim 7 in which said guard circuit is connected to, when closed,maintain the inactive said control magnet energized for said maximumduration of the unguarded period to prevent starting of the inactivesaid unit in response to start operation by said line relay means in theinactive repeater, said slowacting relay being timed to open said guardcircuit at the end of said maximum duration.

10. A two-way start-stop telegraph repeater system in accordance withclaim '7 in which said guard circuit, when closed, includes capacitancemeans to establish a transient energizing current for the inactive saidmagnet in response to a start operation by the inactive said line relayduring the unguarded period, said energizing current being of sufiicientstrength for said maximum duration to prevent starting of the inactive75 said unit, and said slow-acting relay being timed 12. A two-waystart-stop telegraph repeater to open said guard circuit at theexpiration of said maximum duration.

11. A two-way start-stop telegraph repeater system connected forrepeating marking and spacing conditions of signals of a start-stop codebetween two line circuits and comprising a west and an east regenerativerepeater alternately active and inactive to, one at a time, repeat saidmarking and spacing conditions of signals incoming from west and eastinto the east and west line circuits, respectively, each of saidrepeaters in ,cluding receiving Winding means, timed repeating contactmeans controlled as to code by said receiving winding means, lockingcircuit means connected to lock the other of said repeaters againstoperation during the operation of the active repeater, except for anunguarded period during marking condition of greater than apredetermined duration of signals incoming to said active repeater, saidlocking circuit means including guard circuit means connected to locksaid other repeater during spacing condition in response to incomingsignals and timed circuit control means connected to lock said otherrepeater for said predetermined duration under marking condition inresponse to the locking operation or" said guard circuit means.

system connected for repeating marking and spacing conditions of signalsof a start-stop code between two line circuits and comprising a west andan east regenerative repeater alternately active and inactive to, one ata time, repeat said marking and spacing conditions of signals incomingfrom west and east into the east and west line circuits, respectively,each of said repeaters including receiving winding means, timedrepeating contact means controlled as to code by said receiving windingmeans, guard contact means connected to lock the other of said repeatersagainst operation during the operation of the active repeater, exceptfor an unguarded period during marking condition of signals incoming tosaid active repeater, and circuit control means connected to control thestarting of said other repeater and adapted to be operated into one oftwo conditions in response to the locking operation of said guardcontact means and adjustable to automatically remain in said onecondition for a predetermined time interval during said unguarded periodto delay starting of said other repeater.

EDWARD F. WATSON.

